The neuronal ceroid lipofuscinoses (NCLs) are a group of closely related hereditary neurodegenerative disorders which affect infants, children and adults, and which occur at a frequency of between 2 and 4 in 100,000 live births (1, 2). Most forms of NCL afflict children and their early symptoms and disease progression tend to be similar. Initial diagnosis is frequently based upon visual problems, behavioral changes and seizures. Progression is reflected by a decline in mental abilities, increasingly severe and untreatable seizures, blindness and loss of motor skills while further progression can result in dementia or a vegetative state. There is no effective treatment for NCL and all childhood forms are eventually fatal. Several forms of NCL are differentiated according to age of onset, clinical pathology and genetic linkage. These include infantile NCL (INCL, CLN1), classical late infantile NCL (LINCL, CLN2), juvenile NCL (INCL, CLN3) adult NCL (CLN4), two variant forms of LINCL (CLN5 and CLN6) and possibly other atypical forms (1.3). The molecular bases for two of these forms of NCL have recently been identified by positional cloning. Mutations in palmitoyl protein thioesterase (PPT), which removes the lipid moiety from acylated proteins, results in INCL (4). JNCL results from mutations in the CLN3 gene product, a 48 kDa protein of currently unknown function (5). The identity of the molecular lesion in LINCL has remained elusive although the disease gene has recently been mapped to chromosome 11p15 by genetic linkage analysis (3). There are reasons, however, to suspect that the CLN2 gene product could have a lysosomal function. First, LINCL, like other forms of NCL, is characterized by an accumulation of autofluorescent lysosome-like storage bodies in the neurons and other cells of patients. Second, a number of other related neurological disorders are caused by lysosomal deficiencies, e.g. PPT in INCL, neuraminidase in sialidosis and β-hexosaminidase A in Tay-Sachs disease. Third, continuous infusion of leupeptin and other lysosomal protease inhibitors into the brains of young rats induces a massive accumulation of ceroid-lipofuscin in neurons that resembles NCL (6, 7).
Thus, there is a need in the art to identify and characterize the CLN2 gene and its gene product (CLN2).
There is a further need to develop diagnostic and therapeutic applications, based on CLN2, for prenatal testing and treatment of LINCL.
The present invention addresses these and similar needs in the art.
The citation of any reference herein should not be construed as an admission that such reference is available as prior art to the invention.